oxoplasma gondii is an an obligate intracellular protozoan parasite that causes toxoplasmosis.
The infection is worldwide, particularly in warm and moist climates. Domestic cats are the definitive hosts of the parasite and are the main source of infection via oocysts passed in their faeces. Man, livestock and even rodents may act as intermediate hosts for the parasite. Human infection may be acquired by many routes, mainly via contact with infected cats, ingestion of tissue cysts (bradyzoites) in undercooked or raw livestock’s meat.1-4 Human infections in Kuwait were reported to be mainly due to eating or
T
handling desert rodents and goats infected with theparasite.5 The disease may also be transmitted by blood transfusion.
Intrauterine (congenital) transmission may occur.
This may result in hydrocephalus, intracranial calcification and mental retardation in infants born to infected mothers.6 However, most of the toxoplasma infections in adult immunocompetent males or females are either asymptomatic or self-limiting.
The infection is however, severe or fatal in foetus, (as described previously), in patients with acquired immunodeficiency syndrome (AIDS) and in patients Objective: Toxoplasma gondii is an an obligate
intracellular protozoan parasite that causes toxoplasmosis.
The infection is worldwide, particularly in warm and moist climates. Few studies have been conducted on the prevalence of subclinical or overt disease in Saudi Arabia.
No population-based study was conducted or the seroprevalence of toxoplasmosis in humans in Saudi Arabia and this initiated the present study. The present study aimed at studying seroprevalence of Toxoplasma IgG and IgM antibodies in sera from 5 areas in the Eastern Region of Saudi Arabia.
Methods: A population based epidemiological approach, prevalence according to lifestyle (urban or rural), gender (male or female) occupation and age.
Results: Inactive toxoplasmosis (IgG levels) is of rather high prevalence in the human population in the Eastern
Seroepidemiological study of toxoplasma gondii infection in the human population in
the Eastern Region
Abdul R. Al-Qurashi, MSc, PhD, Ahmed M. Ghandour, MSc, PhD, Obied E. Obied, MSc, PhD,
AbdulAziz Al-Mulhim, PhD, Suhair M. Makki, MSc.
From the Department of Microbiology, (Al-Qurashi), Department of Obstetric and Gynecology, (Ghandour), Department of Family and Community Medicine, (Makki), College of Medicine and Medical Sciences, King Faisal University, Dammam, Kingdom of Saudi Arabia.
Received 26th March 2000. Accepted for publication in final form 29th July 2000.
Address correspondence and reprint request to: Dr. Abdul Rehman Al-Qurashi, Department of Microbiology, College of Medicine and Medical Sciences, King Faisal University, PO Box 2114, Dammam 31451, Kingdom of Saudi Arabia. Fax. +966 (3) 8577605.
ABSTRACT
Region of Saudi Arabia (25%). On the other hand, active toxoplasmosis (acquired during pregnancy) is of rather low prevalence in this study (5%). Active toxoplasmosis (IgM levels) is positively related to the level of exposure, high in farmers and employees in village rural areas and low in children and students in urban areas.
Conclusion: Patients with active toxoplasmosis are to be treated and made aware of their situation. Hygienic conditions in areas of rather high prevalence of active toxoplasmosis are to be more strictly imposed to minimize transmission of the disease.
Keywords: Toxoplasma gondii, seroepidemiology.
Saudi Medical Journal 2001; Vol. 22 (1): 13-18
only 4% with acute, (active), infection (IgM) in Abha area.17 Assuming equal distribution between sexes a sample size of 1000-1400 (0-5%) would be adequate for the study (Type I error A=0.05, B=0.2, difference 0.01 and confidence interval 99.9).
Sampling method. A multistage sampling technique was used. Five areas were selected at random: three rural: Al Jisha, Al-Qurain, Al- Nereiyah, and two urban: Al-Mubaraz and Al-Khafji (first stage in sampling). Stratified sampling was used to select at random from each of the five areas (according to population size) one or several segments of houses (second stage in sampling). A group of households were selected at random from each primary segment (selected in the second stage in sampling) and all members in each household were included in the study (third stage in sampling). A total of 1464 sera were collected in the study (804 males and 660 females) (Table 1). A total of 1464 human sera were examined.
Data collection and analysis. The direct blood collection was conducted by the help of trained medical teams (health officers, male and female nurses from the Primary Health Care units in each area of study) under supervision of members of the research team. Blood samples were collected by venepuncture from the subjects in study. A questionnaire was completed by interviewing each subject: age, sex and occupation. The blood samples were carried to the nearest primary health care center, serum prepared, and stored at -20oC for further analysis by the Microparticle Enzyme Immunoassay (MEIA) for IgG and IgM.20,21 In this test IMX Toxo IgG assay results of less than 2.94 IU/mL were considered negative for IgG antibody to T. gondii.
IMX Toxo IgG assay results of greater than or equal to 2.94 IU/mL were considered positive for IgG antibody to T. gondii and may indicate past inactive infection. Serum from subjects positive for IgG were tested for IgM using the same technique: IMX Toxo IgM (MEIA for IgM). IMX ToxoIgM assay indexes of less than 0.500 are negative for IgM antibody to T. gondii. IMX ToxoIgM assay indexes of greater than or equal to 0.500 are considered as positive for IgM antibody to T. gondii and indicate acute active infection.
Methods of statistical analysis. Descriptive statistics was used to describe the quantitative variables. Chi square test, T-test and ANOVA were used as appropriate p values were set to be < 0.05 throughout the study. SPSS version 6 and EPI version 6 were used for data analysis.
Results. The results for seroepidemiological survey of toxoplasmosis in five areas in the Eastern Region are presented in Tables 1-6 and in the following account:
Overall seroprevalence of toxoplasmosis. Of a total of 1464 sera examined from humans living in receiving cytotoxic therapy. In patients with AIDS
and seropositive for toxoplasma 25-50% develop cerebral toxoplasmosis.7 The prevalence of toxoplasma ranges from 7.5-95% in different parts of the world: 7.5% in Scotland,8 50% in USA,9 54% in Kenya,10 47% in Nigeria,11 37% in Jordan,12 and 95.5% in Kuwait.13
Few studies have been conducted on the prevalence of subclinical or overt disease in Saudi Arabia. The toxoplasmin skin test was employed in Riyadh and revealed an overall positivity of 21% in symptomatic and asymptomatic population.14 A case of cerebral toxoplasmosis in an AIDS female patient in Riyadh was reported.15 Recently a high prevalence of toxoplasma (37.5%) (36% of males and 2%
females) using indirect hemagglutination test was recorded in blood donors in Al-Hassa area.16 In the positive cases 35% of the males and 67% of females had a titre of 1/16. The highest seropositivity of antibodies in males were in the age group 21–30 years (48%), followed by the age group 18–20 (25%) and 31–40 years (21%). In females the highest seropositivity was in the age group 18–20 years (40%) followed by 21-30 years (27%) and 31-40 years (20%).
In Abha area, 52% of blood donors were positive for inactive Toxoplasma (IgG in serum) and 4% for active Toxoplasma (IgM).17 Rodents in Riyadh area Mus musculus and Rattus norvegicus, were 12.5%
and 42% positive for Toxoplasma antibodies.18 Tissue cysts of Toxoplasma gondii were recorded in 38 camels’ meat in Al-Ahsa area Eastern Region of Saudi Arabia19 and produced an infection when fed to laboratory bred cats. No population-based study was conducted or the seroprevalence of toxoplasmosis in humans in Saudi Arabia and this initiated the present study. The present study aimed at studying seroprevalence of Toxoplasma IgG and IgM antibodies in sera from five areas in the Eastern Region of Saudi Arabia in a population based epidemiological approach: prevalence according to lifestyle (urban or rural), gender (male or female) occupation and age.
Methods. Study population. This study was conducted in the Eastern Region of Saudi Arabia.
Almost 60% of the population live in rural areas in close contact with livestock and cats. Records of primary health care units in the area showed almost equal distribution between sexes.
Study design. The epidemiological study was population based (not hospital based thus differing from the previous studies of toxoplasmosis in Saudi Arabia). A cross sectional survey was conducted to estimate the seroprevalence of human toxoplasmosis in Eastern Saudi Arabia. Previous surveys of toxoplasmosis in Eastern Region of Saudi Arabia recorded prevalence rate of 37.5% (IgG) in Al-Hassa area,16 51% Inacute Inactive (IgG) in Abha area and
Age (Years)
1-10 11-20 21-30 31-40 41+
Total
Al-Nereiyah
Male No.
23 20 21 20 14
98
Female No.
23 20 20 20 20
103
Al-Qurain
Male No.
25 25 24 24 21
119
Female No.
25 25 25 25 25
125
Al-Khafji
Male No.
20 16 19 20 19
94
Female No.
18 24 20 19 21
102
Al-Jisha
Male No.
22 26 26 26 20
120
Female No.
22 22 22 22 22
110
Al-Mubaraz
Male No.
48 50 44 50 43
235
Female No.
66 70 76 70 76
358 Sex
Table 1 - Sample size of the human sera examined for toxoplasmosis (IgG and (IgM) in all five areas of Eastern Region of Saudi Arabia).
Age (Years)
1-10 11-20 21-30 31-40 41+
Total
No. (%)
132 (9) 137 (9) 134 (9) 140 (9.5)
117 (8)
660 (45)
No. (%)
154 (10.5) 160 (11) 178 (12) 151 (10) 161 (11)
804 (55)
No. (%)
286 (19.5) 297 (20) 312 (21) 291 (20) 278 (19)
1464
Male Female
Table 2 - Overall sample size of human sera examined for toxoplasmosis (IgG and IgM) from five areas in the Eastern Region of Saudi Arabia.
Area of study
Al-Nereiyah Al-Qurain Al-Khafji Al-Jisha Al-Mubaraz
Males
29 (14) 30 (12) 29 (15) 34 (15) 59 (10)
Females
24 (12) 31 (13) 24 (12) 15 (6.5) 89 (15) No. (%) of sera positive for IgG
Males
1 (2) 1 (2) 1 (2) 4 (8) 4 (3)
Females
1 (2) 2 (3) 1 (2) 1 (2) 4 (3) No. (%) of sera positive for IgM
Table 3 - Seroprevalence of toxoplasmosis (IgG and IgM) according to sex in human sera in five areas of study in the Eastern Region of Saudi Arabia.
Area
Al-Nereiyah
Al-Qurain
Al-Khafji
Al-Jisha
Al-Mubaraz
From 5 areas
Type of antibody examined
IgG IgM IgG IgM IgG IgM IgG IgM IgG IgM IgG IgM
No of sera examined
201 53 244 61 196 53 230 49 593 148 1464 364
1-10
8 (4) 0 (0) 6 (2) 0 (0) 5 (2.5) 1 3 (1) 0 (0) 12 (2) 2 (1) 40 (3) 3 (1)
11-20
8 (4) 0 (0) 6 (2) 0 (0) 7 (3.5) 0 (0) 11 (5) 0 (0) 21 (3.5) 2 (1) 53 (4) 3 (1)
21-30
13 (6) 2 (4) 15 (6) 1 (2) 10 (5) 1 (2) 16 (7) 3 (6) 28 (5) 1 (1) 82 (6) 8 (2)
31-40
13 (6) 0 (0) 13 (5) 0 (0) 10 (5) 0 (0) 8 (3) 1 (2) 41 (7) 2 (1) 85 (6) 3 (1)
41+
11 (5) 0 (0) 21 (9) 2 (3) 21 (8) 2 (0) 11 (5) 1 (2) 46 (8) 1 (1) 104 (7) 3 (1) Table 4 - Seroprevalence of toxoplasmosis (IgG and IgM) according to age in human sera from Eastern Region.
Area
Al-Nereiyah
Al-Qurain
Al-Khafji
Al-Jisha
Al-Mubaraz
From 5 areas
Type of antibody examined
IgG IgM IgG IgM IgG IgM IgG IgM IgG IgM IgG IgM
No of sera examined
201 53 244 61 196 53 230 49 593 148 1464 364
Child
5 (2) 0 (0) 1 (0) 0 (0) 3 (1.5)
0 (0) 2 (1) 0 (0) 6 (1) 2 (1) 22 (1.5) 2 (0.5)
Student
8 (4) 0 (0) 7 (3) 0 (0) 15 (10) 1 (2) 14 (6) 0 (0) 26 (4) 2 (1) 70 (5) 3 (1)
Housewife
19 (9) 1 (2) 29 (12) 2 (3) 18 (9) 1 (2) 10 (4) 1 (2) 72 (12) 2 (1) 148 (10) 6 (2)
Employee & farmers
21 (10) 1 (2) 24 (10) 1 (2) 1 (2) 17 (9) 10 (4) 1 (2) 72 (12) 2 (1) 148 (10) 6 (2) Table 5 - Seroprevalence of toxoplasmosis (IgG and IgM) according to occupation.
No. (%) of positive sera
Area of study
Al-Nereiyah Al-Qurain Al-Khafji Al-Jisha Al-Mubaraz
IgG
201 244 196 230 593
IgM
53 61 53 49 148
IgG
53 (26) 61 (25) 53 (27) 49 (21) 148 (25)
IgM
2 (4) 3 (5) 2 (4) 5 (10) 8 (5) Type of antibody
examined
Type of antibody examined Table 6 - A comparison of seroprevalence of toxoplasma (IgG and IgM)
in human sera in five areas of study in the Eastern Region of Saudi Arabia.
samples. However, previous studies in Al-Hassa area and in Abha were hospital based, mainly from blood donors thus not representative of the community in the area. Various epidemiological factors govern the sero-prevalence with toxoplasmosis as indicated in the present study. The prevalence increased with age (considering the pattern of life cycle of the parasite) in the present study and these results are comparable to those in other areas ie. Kuwait.8,13,22,23 The seroprevalence of toxoplasmosis in the present study seems to be also affected by the level of exposure to infection (occupation) since housewives, employees and farmers are more prevalent than children and students. Prevalence with active toxoplasmosis has also been shown well in this study to be related to the degree of life style (urban or rural) and exposure to infection. Similar data was recorded in other endemic areas. Gender does not seem to affect seroprevalence in the areas studied since all five areas and both sexes thus have an equal chance of exposure to infection. Active transmission of Toxoplasma by cats and consumption of bradyzoites in livestock meat is well reported in Al-Hassa area.19 Meat samples from 38 camels in Al-Hassa area fed to four laboratory bred cats resulted in their infection all with toxoplasmosis: oocysts of T. gondii were recorded in their faeces from 9-11 days later and Toxoplasma infection occurred in mice fed on oocysts.
In conclusion, inactive toxoplasmosis (IgG levels) is of rather high prevalence in the human population in the Eastern Region of Saudi Arabia. On the other hand Active toxoplasmosis (acquired during pregnancy) is of rather low prevalence in this study.
Active toxoplasmosis (IgM levels) is positively related to the level of exposure, high in farmers, employees in village rural areas and low in children, students in urban areas. Patients with active toxoplasmosis are to be treated and made aware of their situation. Hygienic conditions in areas of rather high prevalence of active toxoplasmosis are to be more strictly imposed to minimize transmission of the disease.
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